SHIV RESISTANT VARIANTS EMERGE IN AN ELITE NEUTRALIZER MONKEY. We previously reported that one rhesus monkey (CE8J), inoculated with an uncloned preparation of the R5 SHIVAD8-LN, developed potent cross-clade anti-HIV-1 NAbs similar to those observed for HIV-1 infected elite neutralizers. Plasma mapping studies revealed that NAbs in the elite neutralizer CE8J macaque exclusively targeted the HIV-1 gp120 N332 glycan, located immediately downstream of the V3 loop; removal of this glycosylation site from the Env of several HIV 1 isolates eliminated cross-reactive neutralization sensitivity. This broadly reacting neutralizing activity persisted throughout the two-year infection of monkey CE8J. Consistent with several studies reporting a positive correlation between the presence of anti-HIV 1 cross-reacting NAbs and plasma virus load, macaque CE8J, like HIV-1 elite neutralizers, who rarely derive any clinical benefit from the potent cross-reacting NAbs they generate, ultimately succumbed to immunodeficiency and had to be euthanized at week 117 post infection (PI) (Fig. 1) because of chronic Campylobacter coli enteritis. Notably, the virus recovered from this animal at the time of death was resistant to neutralization when tested with plasma specimens collected at weeks 50 and 87 PI. Genetic mapping studies demonstrated that the neutralization resistant SHIVAD8 variants that emerged had acquired substitutions of critical amino acids in the V3 region rather than losing the N332 glycosylation site. One of these resistant variants, carrying the full complement of gp120 V3 changes, was also resistant to the recently described potent anti-HIV 1 monoclonal neutralizing antibodies PGT121 and 10-1074, which are also dependent on the presence of the gp120 N332 glycan. Taken together, our findings show that stepwise substitutions of critical amino acids in the C terminal one-third of the SHIVAD8 gp120 V3 region are sufficient to confer resistance to polyclonal plasma NAbs present in an infected macaque elite neutralizer as well as against two potent monoclonal NAbs, PGT121 and 10-1074, both of which target the N332 glycan. DEGENERATE KIRMHC INTERACTION IN MACAQUES. The killer cell Ig-like receptors (KIRs) expressed on the surface of NK cells recognize specific MHC class I (MHC-I) molecules and regulate NK cell activities against pathogen-infected cells and neoplasia. In HIV infection, survival is linked to host KIR and MHC-I genotypes. In the SIV macaque model, however, the role of NK cells is unclear due to the lack of information on KIR-MHC interactions. In this study, we describe, to our knowledge, the first in-depth characterization of KIR-MHC interactions in pigtailed macaques (Macaca nemestrina). Initially, we identified three distinct subsets of macaque NK cells that stained ex vivo with macaque MHC-I tetramers loaded with SIV peptides. We then cloned cDNAs corresponding to 15 distinct KIR3D alleles. One of these, KIR049-4, was an inhibitory KIR3DL that bound MHC-I tetramers and prevented activation, degranulation, and cytokine production by macaque NK cells after engagement with specific MHC-I molecules on the surface of target cells. Furthermore, KIR049-4 recognized a broad range of MHC-I molecules carrying not only the Bw4 motif, but also Bw6 and non-Bw4/Bw6 motifs. This degenerate, yet peptide-dependent, MHC reactivity differs markedly from the fine specificity of human KIRs.